At each increase of knowledge, as well as on the contrivance of every new tool, human labour becomes abridged.

Whenever the work is itself light, it becomes necessary, in order to economize time, to increase the velocity.

In turning from the smaller instruments in frequent use to the larger and more important machines, the economy arising from the increase of velocity becomes more striking.

There is, however, another purpose to which academies contribute. When they consist of a limited number of persons, eminent for their knowledge, it becomes an object of ambition to be admitted on their list.

The fatigue produced on the muscles of the human frame does not altogether depend on the actual force employed in each effort, but partly on the frequency with which it is exerted.

A tool is usually more simple than a machine; it is generally used with the hand, whilst a machine is frequently moved by animal or steam power.